1. Related Application
This application is related in subject matter to U.S. patent application Ser. No. 275,969, filed Jul. 15, 1994, pending, entitled "Enhanced Methods And Apparatus For Producing Micro-Textured, Thin Film, Magnetic Disc Media And Compositely Micro-Textured Disc Media Produced Thereby", assigned to the assignee of the present application, and identifying Teng, Eltoukhy, Clark, and Goh as co-inventors. The disclosure of this application Ser. No. 275,969, pending is herein incorporated by reference as depicting one preferred mode for practicing the present invention in the context of composite texturing of thin film media.
2. Present Invention
This application depicts a uniquely advantageous application of the sputter induced micro-texturing (SIMT) as described in the above noted, prior application Ser. No. 275,969, pending this present invention being directed to micro-texturing itself produced by the sputtering of eutectically alloyed Indium/Bismuth on an appropriate substrate.
The present invention is characterized by the application of sputter induced micro-texturing utilizing eutectic alloy gloubles of Indium and Bismuth, with the application of this sputter induced micro-texturing (SIMT) not being limited to a multi stage process, as described in the aforesaid application Ser. No. 275,969, pending and either
1) entailing the preconditioning of a normally wettable substrate such as an aluminum substrate treated with nickel phosphorous (NiP), to render the substrate substantially non-wettable so as to enhance the globule formation of the SIMT material, or PA1 2) being applicable to an originally non-wettable substrate, such as glass, etc. PA1 A) providing a disc substrate; PA1 B) sputter depositing a eutectic alloy of Indium and Bismuth upon the substrate to define PA1 C) sputter depositing a thin film of magnetic media upon the roughened, exposed exterior of the substrate with PA1 A) means providing a disc substrate; PA1 B) means for sputter depositing a eutectic alloy of Indium and Bismuth upon the substrate to define PA1 C) means for sputter depositing a thin film of magnetic media upon the toughened, exposed exterior of the substrate, with PA1 A) a disc substrate; PA1 B) a eutectic alloy of Indium and Bismuth sputter deposited upon the substrate to define PA1 C) a thin film of magnetic media sputter deposited upon the roughened, exposed exterior of the substrate, with PA1 the eutectic alloy of Indium and Bismuth having a relatively low melting point relative to the surface energy of the substrate operable to enhance (1) the formation of said discrete globules during the sputtering of said eutectic alloy and (2) the formation and the retention of micro-texturing on the substrate, such being caused by the caused by the presence and at least partial solidification of the globules. PA1 the eutectic alloy of Indium and Bismuth PA1 the eutectic alloy of Indium and Bismuth substantially solidifying as non-transitory, solid phase, generally discrete globules of a eutectic alloy of Indium and Bismuth on the substrate prior to sputter depositing of said thin film magnetic media.
As is noted in the aforesaid U.S. patent application Ser. No. 275,969, pending as the development of thin film magnetic disc media has evolved, certain problems have existed with respect to the attainment of optimal disc operating conditions and magnetic properties.
One particular problem of concern has involved the maintenance of suitable, low friction characteristics on the exposed disc surface, this traditionally being attained by fluid lubricant materials being applied to the disc surface to be read by a magnetic head.
While efforts to apply and maintain such lubricant coatings have engendered substantial research effort, particular attention has been devoted to the formation of roughened or textured media surfaces. These textured surfaces provide alternating arrays of recesses and peaks which are intended to prevent migration of lubricant and undesired, localized lubricant build-up or loss and reduce friction and sticking between the disk and landed head, ie., reduce stiction.
The disadvantage of providing such texturing (usually mechanical) is that it frequently caused undesired, extremely high modulation disparity due to the differences in elevation between portions of the thin film media being traversed by the magnetic head and also tended to cause head damage. (As used herein, the term elevation refers to the difference in displacement of features as measured generally parallel to the axis of disc rotation.)
The present invention is uniquely concerned with the presentation of new and enhanced micro-texturing techniques and apparatus, and the resulting thin film, magnetic media disc product, such being characterized by the attainment of reduced modulation disparity, while effectively controlling the distribution of lubricant during disc operation so as to avoid head sticking problems. These problems commonly are referred to as entailing "stiction", such being produced when heads inadvertently come to rest on disc areas having excessive lubricant accumulation. In addition, optimal head glide characteristics are preserved.
The unique texturing approach of this invention is characterized by SIMT which produces uniform and consistent micro-texturing on appropriate substrates. If such are initially wettable by the SIMT material, i.e., globules of a eutectic alloy of Indium and Bismuth, the substrate is conditioned through the practice of this invention, so as to become generally non-wettable by the SIMT globules, thereby permitting the attainment and maintenance of a surface texturing globule formation.
3. Invention Overview--Presently Preferred Embodiment
In the micro-texturing process of this invention, a eutectic, seed layer formation and micro-texturing treatment is implemented so as to provide a solidified, eutectic alloy, rounded globule-defined, texturing. These solidified eutectic alloy globules comprise a eutectic, Indium and Bismuth alloy.
With respect to the alloy globule features of the present invention, prior art United States patents such as Baseman et al U.S. Pat. Nos. 5,134,038 (1992) and 5,053,250 (1991) do disclose a form of globule formation. However, these IBM patents appear to be restricted to situations where there is an interaction between the magnetic media layer and globules while they are in a transient, liquid stage. No such phenomena as taught by Baseman et al is believed to be involved in connection with the eutectic alloy approach of this present invention. Moreover, the disclosed globule reactivity and disparity in globule size and configuration as disclosed by Baseman et al appear to be effectively avoided by the practice of this present invention.
In addition, a prior U.S. patent application Ser. No. 959,986, filed Oct. 13, 1992, assigned to assignee of this present application, identifying Mahvan et al as co-inventors and entitled "Method And Apparatus For Enhancing The Magnetic And Roughness Properties Of Thin Film Magnetic Recording Media And The Resulting Enhanced Media" discloses the use of certain peritectic alloys which are sputter deposited to form texturing on initially non-wettable substrates such as glass. Neither the eutectic Indium/Bismuth alloy of this invention nor the substrate conditioning step of one preferred embodiment of this invention are contemplated in this prior application.
4. General State Of The Art Summary
By way of summarizing the general state of the art, the following compilation of United States patents, and a Pilkington EPO application, generally are indicative of the various approaches which have been pursued in connection with micro-texturing technology. In this compilation, at the end of each patent title, a code has been applied, generally indicating the principle nature of the disclosure and claimed subject matter, with the meaning of these codes being identified in the code table at the end of the patent listing.
__________________________________________________________________________ ITEM NUMBER INVENTOR ASSIGNEE TITLE (SUBJECT) __________________________________________________________________________ EPO Application 579,399,A2 Wilson et al Pilkington Brothers, Glass Substrate For A Magnetic PLO Disc And Manufacture Therefore (ME) U.S. Pat. No. 3,019,125 Eggenberger et al IBM Thin Magnetic Film (CG) 3,193,362 Hespenheide Burroughs Corp. Magnetic Materials (M) 4,326,229 Yanagisawa Nippon Electric Co. Magnetic Record Member And Process For Manufacturing The Same (M) 4,499,122 Economy et al IBM Process For Finishing Surfaces Achieving Improved Magnetic Disk Performance (P) 4,616,237 Pettigrew et al Pa Management Data Storage Medium (CG) Consultants, Ltd. 4,675,075 Sakai et al Fujitsu Limited Magnetic Recording Production Processes (ME) (H) 4,698,251 Fukuda et al Victor Company of Magnetic Recording Medium And Japan, Limited Method Of Producing The Same (CG) 4,724,444 Pettigrew et al Plasmon Data Data Storage Medium (CG) Systems, Inc. 4,734,810 Nakayama et al TDK Corporation Magnetic Recording Medium Comprising Protrusion On Its Surface And A Plasma Treated Substrate And Recording/Reproducing Method Therefor (PE) 4,375,840 Hedgcoth Cyberdisk, Inc. Magnetic Recording Disk And Sputtering Process And Apparatus For Producing Same (CG) 4,828,899 Arioka et al TDK Corporation Magnetic Recording Medium And Recording/Reproducing Method Thereof (P) 4,833,001 Kijima et al Asahi Glass Glass Substrate For A Magnetic Company, Ltd. Disc And Process For Its Production (CE) 4,894,133 Hedgcoth Virgle L. Hedgcoth Method And Apparatus Making Magnetic Recording Disk (CG) 4,925,738 Tsuya et al -- Substrate For A Magnetic Disk And Process For Its Production (PO) (CE) 4,393,614 Shirakura et al Hitachi, Ltd. Magnetic Disk Medium With Circumferentially Textured Surfaces And Varied Surface Roughness And Method Of Producing Same (CG) 4,973,496 Kruger et al IBM Method For Texturing Magnetic Disks (CG) 4,985,306 Morizane et al -- Base Plate For Recording Disk And A Method For Its Manufacture (CE) 4,996,622 Takatsuki et al Nippon Sheet Glass Magnetic Disk With Textured Co., Ltd. Area On Part Of Disk (CG) 5,047,274 Tsuya et al -- Annodized Aluminum Substrate For A Magnetic Recording Disk In Which Pores Are Filled With A Non Magnetic Material And The Surface Polished And Etched (PP) 5,053,250 Baseman et al IBM Thin Film Magnetic Medium With Controlled Grain Morphology And Topology For Improved Performance (G) 5,062,021 Ranjan et al Magnetic Selectively Textured Magnetic Peripherals, Inc. Recording Media (L) 5,070,425 Inumoch Mitsubishi Denki Surface Structure Of A Magnetic Kabushiki Kaisha Disk (CG) 5,074,971 Tsuya et al -- Process For Preparing Magnetic Disk (PO) (CE) 5,079,062 Masuda et al Hitachi, Ltd. Magnetic Recording Medium Having A Thin Film Magnetic Layer Formed Over a Non-Magnetic Substrate Which Has Powder Grains Of The Substrate Dipsosed On Its Surface (P) 5,082,709 Suzuki et al Matsushita Electric Thin Film-Type Magnetic Disk (P) Industrial Co., Ltd. 5,082,747 Hedgcoth -- Magnetic Recording Disk And Sputtering Process And Apparatus For Producing Same (CG) 5,087,481 Chen et al Komag, Inc.; Asahi Method For Texturing A Magnetic Glass Co., Ltd. Disk Silicate Glass Substrate (CE) 5,087,482 Kawai et al Hoya Corporation Method Of Manufacturing Magnetic Recording Medium Capable Of Recording Information At A High Recording Density (P) 5,091,225 Goto NEC Corporation Magnetic Disk Member And Process For Manufacturing The Same (P) 5,093,173 Nakagawa et al Hitachi, Ltd. Magnetic Disk Comprising A Substrate Of An Amorphous Glass Continuous Phase Dispersed With Crystal Particles Which Produce A Structurally Defined Surface On The Substrate (CE) 5,108,781 Ranjan et al Magnetic Process For Manufacturing Peripherals, Inc. Selectively Textured Magnetic Recording Media (L) 5,108,812 Takahashi et al -- Substrate For A Magnetic Disk And Process For Its Production (PP) 5,119,258 Tsai et al HMT Technology Magnetic Disk With Low-Friction Corporation Glass Substrate (PE) 5,134,038 Baseman et al IBM Thin Film Magnetic Recording Medium With Controlled Grain Morphology And Topology (G) 5,166,006 Lal et al HMT Technology Textured Thin-Film Substrate And Corporation Method (P) 5,209,837 Tsuya et al -- Process For Preparing Magnetic Disk (PE) (CE) 5,210,673 Ito et al Hitachi Metals, Ltd. Thin-Film Hard Disk Magnetic Medium (CG) 5,223,304 Yasuda et al Sumitomo Metal Process For Fabricating Magnetic Mining Company, Ltd Disks (P) 5,225,955 Ito et al Hitachi Metals, Inc. Disk-Shaped Magnetic Recording Medium Having Novel Textured Surface (CG) 5,232,750 Onodera et al Fuji Electric Co., Ltd. Method For Fabricating Magnetic Recording Medium (US) 5,250,339 Tani et al Nihon Shinku Magnetic Recording Medium (CG) Gijutsu Kabushiki Kaisha 5,268,207 Kruger et al IBM Texturing The Surface Of A Recoridng Disk Using Particle Impact (US) 5,285,343 Tanaka et al Hitachi, Ltd. Magnetic Disk With Surface Protective Layer Having Convex Portions And Magnetic Disk Apparatus Including Such A Magnetic Disk (CE) 5,316,864 Hedgcoth -- Sputtered Magnetic Recording Disc __________________________________________________________________________ (CG) CODE TABLE CEChemical Etching CGCircumferential Grooving GGlobule HHeat LLaser MMiscellaneous Mechanical MEMasking/Etching PParticles PEPlasma Etching POPores PPPore Packing USUltra Sonic